Variation in aggressive behavior and anatomo-physiological correlates generated by crowding without physical contact in the house mouse

Behavioral, physiological (i.e., endocrine), and anatomical consequences of crowding in mice were studied in a situation where animals were in auditory, visual, olfactory, and tactile contact but restrained from full physical interactions, to prevent overt aggression. Males that cohabited with females undisturbed by neighboring conspecifics showed greater propensity to attack same-sex intruders and had higher plasma testosterone levels than did their “crowded” counterparts, that is, males cohabiting with females and housed adjacent to other male/female pairs. In this respect, the latter animals resembled submissive males. However, a significant increase in weight of androgen-dependent target organs (i.e., seminal vesicles and preputial glands) was found in crowded males. These data indicate that despite the observed inhibition of social aggression these males are not physiologically comparable (homologous) to male mice that experienced defeat and the stress of submission during fighting. The intriguing possibility that different conversion pathway of testosterone are accelerated, as a result of social communication, in males living in these two environments and the behavioral implications of these possibilities are discussed. Finally, the parental behavior of crowded animals, although not freely interacting with each other, was disrupted, causing a marked decrease in reproductive success. In this situation a high incidence of infanticide of their offspring by both parents was observed, whereas this behavior was virtually absent in non-crowded male/female pairs.     

Attention enhances apparent perceptual organization

Perceptual organization and selective attention are two crucial processes that influence how we perceive visual information. The former structures complex visual inputs into coherent units, whereas the later selects relevant information. Attention and perceptual organization can modulate each other, affecting visual processing and performance in various tasks and conditions. Here, we tested whether attention can alter the way multiple elements appear to be perceptually organized. We manipulated covert spatial attention using a rapid serial visual presentation task, and measured perceptual organization of two multielements arrays organized by luminance similarity as rows or columns, at both the attended and unattended locations. We found that the apparent perceptual organization of the multielement arrays is intensified when attended and attenuated when unattended. We ruled out response bias as an alternative explanation. These findings reveal that attention enhances the appearance of perceptual organization, a midlevel vision process, altering the way we perceive our visual environment.     

Biological relevance of acoustic signal affects discrimination performance in a songbird

The fee-bee song of the black-capped chickadee (Poecile atricapillus) is a two-note, tonal song that can be sung at different absolute pitches within an individual. However, these two notes are produced at a consistent relative pitch. Moreover, dominant birds more reliably produce songs with this species-typical interval, compared to subordinate birds. Therefore, we asked whether presenting the species-typical relative pitch interval would aid chickadees in solving pitch interval discriminations. We found that species-typical relative pitch intervals selectively facilitated discrimination performance using synthetic sine-wave stimuli. Using shifted fee-bee song notes from recordings of naturally produced songs, birds learned the discrimination in fewer trials overall compared to synthetic stimuli. These results may reflect greater generalization among stimuli that occur outside species-typical production parameters. In addition, although sex differences in performance are rarely observed in acoustic discriminations in chickadees, female chickadees performed more accurately compared to males.     

Black-capped chickadee (Poecile atricapillus) and human (Homo sapiens) chord discrimination

Human music perception is related both to musical experience and the physical properties of sound. Examining the processing of music by nonhuman animals has been generally neglected. We tested both black-capped chickadees and humans in a chord discrimination task that replicates and extends prior research with pigeons. We found that chickadees and humans, in common with pigeons, showed similar patterns of discrimination across manipulations of the 3rd and 5th notes of the triadic chords. For all species (chickadee and humans here, pigeons previously), chords with half-step alterations in the 5th note were easier to discriminate than half-step manipulations of the 3rd note, which is likely due to the sensory consonance of these chords. There were differences among species in terms of the fine discrimination of the chords within this larger pattern of results. Further, the ability to relearn the chords when transposed to a new root differed across species. Our results provide new comparative data suggesting some similarities in chord perception that span a wide range of species, from pigeons (nonvocal learners) to songbirds and humans (vocal learners).     

Pitch chroma discrimination, generalization, and transfer tests of octave equivalence in humans

Octave equivalence occurs when notes separated by an octave (a doubling in frequency) are judged as being perceptually similar. Considerable evidence points to the importance of the octave in music and speech. Yet, experimental demonstration of octave equivalence has been problematic. Using go/no-go operant discrimination and generalization, we studied octave equivalence in humans. In Experiment 1, we found that a procedure that failed to show octave equivalence in European starlings also failed in humans. In Experiment 2, we modified the procedure to control for the effects of pitch height perception by training participants in Octave 4 and testing in Octave 5. We found that the pattern of responding developed by discrimination training in Octave 4 generalized to Octave 5. We replicated and extended our findings in Experiment 3 by adding a transfer phase: Participants were trained with either the same or a reversed pattern of rewards in Octave 5. Participants transferred easily to the same pattern of reward in Octave 5 but struggled to learn the reversed pattern. We provided minimal instruction, presented no ordered sequences of notes, and used only sine-wave tones, but participants nonetheless constructed pitch chroma information from randomly ordered sequences of notes. Training in music weakly hindered octave generalization but moderately facilitated both positive and negative transfer.     

Chickadees fail standardized operant tests for octave equivalence

Octave equivalence occurs when an observer judges notes separated by a doubling in frequency perceptually similar. The octave appears to form the basis of pitch change in all human cultures and thus may be of biological origin. Previously, we developed a nonverbal operant conditioning test of octave generalization and transfer in humans. The results of this testing showed that humans with and without musical training perceive the octave relationship between pitches. Our goal in the current study was to determine whether black-capped chickadees, a North American songbird, perceive octave equivalence. We chose these chickadees because of their reliance on pitch in assessing conspecific vocalizations, our strong background knowledge on their pitch height perception (log-linear perception of frequency), and the phylogenetic disparity between them and humans. Compared to humans, songbirds are highly skilled at using pitch height perception to classify pitches into ranges, independent of the octave. Our results suggest that chickadees used that skill, rather than octave equivalence, to transfer the note-range discrimination from one octave to the next. In contrast, there is evidence that at least some mammals, including humans, do perceive octave equivalence.     

Beyond Deficits: Intimate Partner Violence,Maternal Parenting,and Child Behavior Over Time

Exposure to intimate partner violence (IPV) has negative consequences for children’s well-being and behavior. Much of the research on parenting in the context of IPV has focused on whether and how IPV victimization may negatively shape maternal parenting, and how parenting may in turn negatively influence child behavior, resulting in a deficit model of mothering in the context of IPV. However, extant research has yet to untangle the interrelationships among the constructs and test whether the negative effects of IPV on child behavior are indeed attributable to IPV affecting mothers’ parenting. The current study employed path analysis to examine the relationships among IPV, mothers’ parenting practices, and their children’s externalizing behaviors over three waves of data collection among a sample of 160 women with physically abusive partners. Findings indicate that women who reported higher levels of IPV also reported higher levels of behavior problems in their children at the next time point. When parenting practices were examined individually as mediators of the relationship between IPV and child behavior over time, one type of parenting was significant relationship, such that IPV lead to higher authoritative parenting and lower child behavior problems. On the other hand, there was no evidence that higher levels of IPV contributed to more child behavior problems due to maternal parenting. Instead, IPV had a significant cumulative indirect effect on child behavior via the stability of both IPV and behavior over time. Implications for promoting women’s and children’s well-being in the context of IPV are discussed.